I tried the fix from RooieDirk to recover lost tracks. First saved the .xml files to a new folder. Then before changing the name of navobj.xml.5 deleted navobj.xml.
Did not recover the lost track this way but recent new Routes were lost after I put the old saved .xml files back in place. Any suggestions?

As you have saved all the navobj files, try navobj.xml1 - this is the most recent one.
xml5 is the sixth generation (xml(0) --> xml5)

More: The xml files are user readable. Open it with a decent editor like Notepad++, not with the Windows onboard Notepad, and you can cherrypick routes and tracks and copy them back into the actual xml file.
But be sure what you are doing! Always with a back-up at hand.

BCN and Gerhard,
Tried your suggestions and learned something again but no luck in retrieving the track. OpenCPN really crashed while I was reorganizing tracks and the ones I was working on completely disappeared. Nothing to do about it.
Thanks for your help!